Energy efficient system design in portable, battery-operated electronic devices has become increasingly important since energy consumption dictates the battery lifetime of a portable system, and this is a crucial performance metric for the success of any product in the consumer market. Thus, power management is becoming an indispensable part of the system infrastructure.
Dynamic power management (DPM) is a design methodology that enables the dynamic configuration or reconfiguration of a system for energy or power efficient computation. In “A Survey of Design Techniques for System-Level Dynamic Power Management” IEEE Transactions on VLSI Systems, Vol. 8, No. 3, June 2000 by L. Benini, A. Bogliolo and G. de Micheli, several DPM techniques are discussed. These techniques involve switching off or ‘slowing down’ idle parts of the system, and dynamically trading system performance for energy efficiency. DPM techniques provide ways to optimize and control the system power by tuning the performance of the individual system components to the varying workload.
In systems with a dynamically varying workload, that is, in systems that do not have to deliver a peak or maximum performance all of the time, the voltage and clock frequency can be controlled to optimise the power consumption of the system. This is known as dynamic voltage and frequency scaling (DVFS).
Many techniques have been proposed in literature for such systems, mostly scaling the voltage and frequency depending on the performance requirements. For example, in “Dynamic Voltage Scaling on MPEG Decoding” by D. Son, C. Yu and H. Kim an application based technique is proposed in which the voltage and frequency are adjusted depending on the decoding performance of the application.
Where the system is used to process a data stream with a high degree of parallelism, such as a stream of image data, single-instruction multiple-data (SIMD) processors can be used. The SIMD processor exploits the parallelism in the data stream to permit a lower operating frequency and memory localisation, which translates into lower power dissipation relative to a single-instruction, single-data processor operating on the same data stream.